Add --ignore-unknown flag to Prettier

During `common-good fix-staged` we fail when we see files like `foo.png`
staged, because Prettier doesn't know how to write to them. Instead, we
should just ignore those files so that we don't fail pre-commit tests.

config/lint-staged-fix.js

@@ -2,7 +2,7 @@ const eslintConfig = require.resolve("./eslint.js");
 const stylelintConfig = require.resolve("./stylelint.json");
 
 module.exports = {
-  "*": "prettier --write",
+  "*": "prettier --ignore-unknown --write",
   "*.css": `stylelint --config ${stylelintConfig} --fix --allow-empty-input`,
   "*.{js,jsx,md,ts,tsx}": `eslint -c ${eslintConfig} --fix`,
 };

config/lint-staged-test.js

@@ -4,5 +4,5 @@ const stylelintConfig = require.resolve("./stylelint.json");
 module.exports = {
   "*.{js,jsx,md,ts,tsx}": `eslint -c ${eslintConfig}`,
   "*.css": `stylelint --config ${stylelintConfig} --allow-empty-input`,
-  "*": "prettier --check",
+  "*": "prettier --ignore-unknown --check",
 };

index.js

@@ -22,12 +22,12 @@ const stylelintConfig = require.resolve("./config/stylelint.json");
 const testCommands = [
   `eslint -c ${eslintConfig} **/*.{js,jsx,md,ts,tsx}`,
   `stylelint --config ${stylelintConfig} --allow-empty-input **/*.css`,
-  "prettier --check .",
+  "prettier --ignore-unknown --check .",
   "depcheck",
 ];
 
 const fixCommands = [
-  "prettier --write .",
+  "prettier --ignore-unknown --write .",
   `eslint -c ${eslintConfig} --fix **/*.{js,jsx,md,ts,tsx}`,
   `stylelint --config ${stylelintConfig} --fix --allow-empty-input **/*.css`,
   "depcheck",